William Whitelaw, 1st Viscount Whitelaw Signed 1973 letter

Wiki states "William Stephen Ian Whitelaw, 1st Viscount Whitelaw, KT, CH, MC, PC, DL (28 June 1918 - 1 July 1999), often known as Willie Whitelaw, was a British Conservative Party politician who served in a wide number of Cabinet positions, most notably as Home Secretary and de facto Deputy Prime Minister. He was Deputy Leader of the Conservative Party from 1975 to 1991"